Other than JP to Honor conversion and Transmog gear, you can stock up JP in the hope that Item Upgrading returns in Patch 5.3. Upgrade all the 463ilvl gear if you don't have better, or upgrade the new Mantid Archeology items for alts.
As well, if you have a Jewelcrafter, you can purchase Epic Wrath gems for ~200 and make cuts. It's a niche market, but on high population realms you can make a small profit.

You notice how in this patch, blizzard removed the item upgrade vendor because they didn't want to make it easy for people to upgrade before they.. you know, UPGRADE. Well given how they feel its ok to switch aspects they introduce on and off so freely, why then can't they invent a system where if your character is in higher ranking gear that he can't buy anything better with justice points, he can then transfer his JP to another character would could use it, like say post 1k jp to an alt once per day.